The present invention pertains to a sheet feeding or delivering device and, more particularly, to an improved brush assembly for use in the deceleration section of a sheet conveying system.
Sheet conveying and handling systems often include a deceleration section where serially aligned sheets leaving an upstream conveyor are compressed and shingled on a slower moving downstream receiving conveyor. One common type of decelerating or shingling conveyor utilizes a vacuum belt which serves to capture the faster moving sheets from the upstream conveyor and hold them onto the vacuum belt of the slower moving deceleration conveyor. Depending upon sheet length, speed, and the material from which the sheets are made, a vacuum deceleration conveyor may alone be insufficient to provide adequate sheet deceleration and to maintain control of the sheet.
Various devices to assist the transfer of sheets onto a vacuum deceleration conveyor are known in the art. One common device is an arrangement of one or more brushes, each of which extends across the conveyor perpendicular to the direction of sheet travel and positioned to bring a line of flexible brush bristles into bearing contact with the upper surfaces of the sheets as they are delivered into the vacuum conveyor section. The brush or brushes assist in providing a frictional decelerating force to the sheets and also to press the sheets downwardly onto the vacuum conveyor because of the inherent resilience of the bristles. Such brush assemblies often include means for adjusting the angle and amount of bristle contact with the sheets to selectively vary the force imposed by the brushes.
Typical prior art sheet deceleration devices including brushes are shown in U.S. Pat. Nos. 3,998,141, 4,133,523, 4,667,953, and 5,599,012. Plastic fiber bristles are often used in such brushes, but little attention has been paid in the prior art to the particular selection of plastic resins from which such bristles are made. Bristles or strips made of polyurethane, nylon, neoprene and other common plastics are known, However, a characteristic common to all of these materials is that, in use and under load, whether constant or varying, prior art plastic bristles wear rapidly from contact with abrasive paper sheets and quickly take a permanent set reflecting the bend to which they are subjected in use. Both the reduction in bristle length because of wear and the effective change in bristle position because of a permanent set in the bristles change the performance of the brushes and eventually require readjustment of the brush positioning system or replacement of the brush.
U.S. Pat. No. 5,139,862 discloses electrically conductive flexible pultruded fibers which are used to make a brush-like contact for an electrical switch. No use of these fibers in a brush assembly for a sheet handling system is described or suggested.